Purification of organic compounds



Aug L 1933 A. o. JAEGER PURIFICATION OF ORGANIC COMPOUNDS 1927 14 Sheets-Sheet l Original Filed Nov. 2l

A. O. JAEGER Aug. l, 1933.

PURIFICATION OF' ORGANIC COMPOUNDS original Filed Nov. 21, 1927 14 Sheets-Sheet 2 l i 1G53 A. Q. JAEGi-Qm Original Filed Nov. 2l, 1927 3.4 SheGSWSl'lee 5 NVENTOR /ID on5 O. kmayer ATTORNEY Aug E w33- A. o. JAEGER PURIFICATION OF ORGANIC COMPOUNDS 1927 14 Sheets-Sheet 4 Original Filed Nov. 2l

andamio@ /.lohons O eyer toznm Aug i, 3933 A. o. JAEGER PURIFICATION OF ORGANIC COMPOUNDS Original Filed Nov. 2l, 1927 14 vSheets-Sheet 5 INVENTOR 7 eye/- ATTORNEY u 1933. A'. o. JAEGER PURIFICATION OF ORGANIC COMPOUNDS Original Filed Nov. 2l, 1927 14 Sheets-Sheet 6 INVENTOR ,4170/10/75 O- Jaeyer ATTORNEY ug. l, 1933. A. 0* JAEGER LQZQS PURIFIOATION OF ORGANIC COMPOUNDS Original Filed Nov. 2l, 1927 14 Sheets-Sheet 7 ai 4# Vjtgs INVENTOR mmm ATTORNEY Auge 1933i A Q JAEGER Lggg@ PURIFICATION OF ORGANIC COMPOUNDS Original Filed Nov. 2l, 1927 14 Sheets-Sheet 8 ugl 933- A, o. JAEGER PURIFICATION OF ORGANIC COMPOUNDS Original Filed Nov. 2l, 1927 14 Sheets-Sheet 9 unulnnnn x/ 57776 yd y LJ F/G. I8.

ATTORNEY Aug- 1 1933 A. o. JAEGER PURIFICATION OF ORGANIC COMPOUNDS 14 Sheets-Sheet lO I Original Filed NOV. 21, 1927 INVENTOR //o/zons O. Jaeger ATTORNEY ug. E., A Q JAEGER PURIF'ICATION OF ORGANIC COMPOUNDS Original Filed Nov. 2l, 1927 14 Sheets-Sheet ll F/G. ZZ

INVENTOR HLp/rons O. Jaeger ATTORNEY ug E, A C)` JAEGER PURIFICATION OF ORGANIC COMPOUNDS Original Filed Nov. 2l, 1927 y 14: Sheets-Sheet l2 INVENTOR ATTORNEY Aug. l, 1933. A. o. JAEGER PURIFICATION OF' ORGANIC COMPOUNDS Original Filed Nov. 21, 1927 14 Sheets-Sheet 13 INVENTOR ,4L/06005 O. Jeyer ATTORNEY Aug' l, 1933- A. o. JAEGER 1.920,796

PURIFICATIONOF ORGANIC COMPOUNDS Original Filed Nov. 21, 1927 14 ASheecs-Smeet 14 ATTORNEY Patented Aug; 1,1933

hgiit 1,920,798v 'PUltllFlCA'lllUN 0F GRGANIC CQIVEOEJNBS Illphons 0. Jaeger, Mount Lebanon, lia., 4assigner to The Selden Company, Pittsburgh, Pa., a Corporation of Delaware originan application Newman-21, naar,A serial' Divided and this application September' 28, i929. Serial No. 395,967

5i claims. (ci. 2st-ice) This invention'relates to processes of carrying out vapor phase catalytic oxidations of organic compounds and particularly such oxidations which by reason ofy the rinstability of the products produced or the heat evolved require close temperature control.

Many catalytic organic oxidations are strongly exothermic and require eliicient cooling means to control the reaction and a number V.oi the reactions are also sensitive `by reason ci thev iact that in many cases intermediate products are obtained which are Arelatively unstable and tend to oxidize further unless the reaction conditions and particularly the tern' erature are carefully controlled. ln the case of certain oxidation reactions in Which a mixture of compounds are purified by the total combustion of certain impurities, a good temperature control isalso necessary as in many cases the products which it is desired to leave intact tend to become oxidized if the temperature is unduly raised. The necessity of better temperature control and in many cases the removal of large amounts of heat in strong exothermic oxidations has necessitated in the past the use of many elaborate schemes and also the use oi expensive andfrequently vdelicate and complicated apparatus. Thus, for example, many catalytic'organic reac l tions have hitherto been carried out in converters provided with a large numbei` oi Vvery small tubes surrounded by powerful cooling agents, for

example, baths'boiling or non-boiling. Many of these converters arev very expensive owing to their great complexity and present numerous disadvantages as it is diicult to keep suchv structures. tightand the baths used for cooling, par'- ticularly when mercury or mercury alloys are used; require absolute. tightness because the method ofcooling `in which reaction gases iurv nish the mainor primaryfcooling means and are circulated inheat exchanging relation to the cat- `alyst ini-such a manner'as to produce automatic heat control. This is eliected in thepresent invention broadly by causing the reaction gases to circulate in double countercurrent, nrst in indirect heat exchanging relation with the catalyst then, afterreversal of flow, in direct heat eX- changing relation With the catalystl and, nally,

after a second reversal of flow, topass through the catalysts. Preferably the rst flow in indirect heat exchanging `relation with the catalysts is also indirect heat exchanging relation with the counter flow of the gases. This may be eected either by circulating the gasesthrough a large number of small, preferablytubular or square heat exchanging elements embedded in a catalyst layer or other arrangements and types or heat exchanging elements and catalyst layer may be used which produce the same type of cooling gas flow. A number of themodications and modi fled forms oi apparatus in which the principles of the present invention can be used are illus-- trated in the drawingsin'diagrammatic form. 70

converter construction eliminating4 by'far the 'g5 if greater number oi WeldedA or gas-tight connections and it also presents great advantagesin operation. First, relatively large catalyst layers are used which at once solves the problem of uni form catalyst permeability so serious when a go large number of relatively small tubes are used.- The second very vital advantage lies in the fact that reaction gases in cooling the catalyst' are themselves gradually uniformly and efficiently heated up to the necessary reaction temperature` g5 without the necessity of using additional fuel.

IThe most important advantage of the present invention lies yin the feature of automatic cooling. The heat evolved in vapor phase organic catalytic oxidations is directly proportional to the amount of reaction` gases passed through the catalyst in a unit time, assuming substantially uniform conversion. The amount of primary cooling used in the present invention in Which'the reaction gases themselves constitute the 'cooling 95 medium is also directly proportional to the` Vamount of reaction gases owing through. Therefore; once suitably adiustedkior a given reaction the cooling is automatic and does not vary with uctuations in loading over Wide limits `determined only by the range-of loadings giving substantially uniform conversions. and by the 'cooling factor of converter structure, such as the converter shell which in some cases can be substantially eliminatedv by thorough insulation or suitable heating. This featureis of the utmost importance in sensitive organic oxidations for it is in some cases difficult and in many casesimpossible to provide for a lperfectly uniform flow of reaction gases through the catalyst at all times.

Fluctuations, which in practical operation are frequently unavoidable, are automatically equalized by the cooling principles of the present invention. There is no danger therefore of fiu'c-j tuations in the loading raising the temperature of the catalysts, which frequently tends to cause the oxidation to become uncontrollable and consti,-

tutes a serious problem in organic reactions due to the fact thatV frequently small increases in cat-3 alyst temperature will tend to greatly vary the 'course of the reaction, usually resulting in a greater amount of total combustion with a correspondingly still greater increase in heat, In other words the average organic oxidation, Whether to an intermediate product or for the purpose of catalytically burning out certain selected impurities, is in unstable equilibrium and sudden increases in loading with concomitant evolution of heat tend to cause the reaction to become uncontrollable as the effects of increased loading become cumulative. It is for this reason thatmany converters used in the prior art have such powerful cooling means, asv boiling baths, in order to preventlreactions from becoming uncontrollable. The problem is solved by means of the present invention with its automatic cooling feature in a simple and elegant manner.

It should be understood that it is not necessary to circulate allA of the reaction gases in double counter-current heat exchanging relation with the catalyst although for many reactions this'isfthe preferred method. In some reactions, however, it is desirable to heat up only a portion of the reacting gas and in such cases a portion only may be circulated in heat exchanging rela- `tion with the catalyst. yIn other cases it maybe undesirable to subject certain of the reaction components to Contact with the hot surfaces of the heat exchanger which, usually for the sake of cheapness, are made of iron, aluminum or steels.

In such cases the "air or'oxidizing gas may be cir-v culated through vthe heat exchangers and the organic substances maybe introduced directly at any desirable temperature. Further modica tions of ow may be usedfor chemical reasons `or to improvethe temperature control.

While it is an important advantage of the present inventionthatin the case of many reactions the simple automatic method of cooling by means ofthe reaction gases ina counter-current heat exchange with the catalysts may-be used to control the reaction in an elegantly simple manner, the invention is in no sense limited to the use of this cooling means as the sole method of controlling the reaction and it may be associated with other methods, such as for example heat equalizing elements, which maybe of homogeneous composition and high heat conductivity or which may contain liquids, whether Yboiling or non-boiling. Such means maybe used to remove a portion of the exotherm of the reaction or they may servesolely the'purpose of maintaining or equalizing thev heat throughout v.the catalyst.

portance in the controlling of many delicate reactions. A number of these auxiliary means are illustrated diagrammatically in the drawings and it is understood that theprinciple of the present invention may be applied either alone or in conjunctionvwith other cooling or temperature controlling means whether new 01 old and it is an advantage of the present invention that it is extremely flexible and its principle may be utilized in conjunction with various types of converter structure."'Ihe extent Vto which the principles Vo1"- the invention are used andthe absence or choice of auxiliary cooling media in all cases will be determined by the skilled chemical engineer after a careful consideration of the requirements of the particular reaction or installation involved.

The great flexibility of the present invention permits a very uniform cooling of the catalyst by suitable placement of heat exchange elements, with uniform or non-uniform gas flows, and it is thus possible in many cases to achieve not only a total control of reaction but also a uniformity of reaction throughout the catalyst or zones thereof which is of great importance in increasing the yield and also in many cases in prolonging the life of the catalyst.

' The automatic cooling provided in the present invention permits, as has been pointed out above, great variations of load and in many cases this may be translated into increased out-put. However, in some cases it may be desirable to restrict the out-put in order to still further improve the temperature control and the efciency of the control inthe present invention may therefore be used to either permit a greater loading, that is to say a greater gross out-put, or they may be used to provide a better percentage yield at the same gross out-put. In every case, however, an improved total output is obtained and the particular use which is made of the cooling features of the present invention must of course be dictated by the requirements of the'particular reaction and the particular installation. 'Ihe great flexibility of the present invention is of practical importance in its application to a wide field of catalytic organic oxidations.

The present invention has been described above more particularly in conjunctionY with highly exothermic organic'oxidations and some of its most important applications are to be found in this field. It should be understood, however, that the present invention does not in its broader scope cover merely a cooling means but on the contrary should be considered as a temperature controlling means and even in reactions which are so slightly exothermic as to render outside heat necessary the principles of the present invention are equally applicable even though it may not be possible to save the yuse of fuel for heating. The present invention provides for a very reliable temperature control preventing not only excessive ternperaturesv but tending also to prevent the temperature dropping too low and permitting the greatest possible utilizationvof thel heat of reaction.

The invention will bedescribed in greater detail in connection with a number of representative `nea'ofree purely diagrammatical in nature and Vin many cases may -be considered almost inf the light of reaction flow sheets. It should beV understood, o1'

1 course. that theskilled chemical engineer will design his converter and choose his apparatus `accessories in accordance with thebest practice ofthe art, -iollovving the principles outlined in the present invention. v l

In the drawingszf Fig. 1 is a vertical cross section through a converter showing the V.automatic gas cooling feature of thel present invention; Fig. 2 is a horizontalcross section throug Fig.,-1; i

Figs. 3 and 4 are detailsl of the method of supporting the heat exchange elements;

Fig. '5 is a vertical section through a modified converter of theytype shown in Fig, 1;v Fig. 6 is a vertical section through La converter having an internal heat exchanger.;

' Fig. 7 is a vertical section through a converter With double heat exchange elements; v

Figs. 8 andl 9 are vertical sections through a modified converter provided with auxiliary gas introducing means. f

. Fig. 10 is a detail ofthe gas distributors shown Vin Fig.l 9

Fig. V1l is a Adetail of a converter `withmodified heat exchanger construction;

and internal heat exchanger; f

Figs. 12 and 13are details of heat equalizing means shown in Figs.gl5, 16,17, 18, 25 and 28;

Fig. 14 is a vertical section througha converter showing recirculating means;

f Figs. 15 and 16 are vertical and horizontal sections through a converter showing bothv circulationand `heat equalizer means;

Fig. 17 is a vertical section throughl a modiiied type of converter or" the general type shown in Figs. 15 and 16; I

Fig. 18 is a vertical section through a converter shovving circulatingrmeans with external cooler Fig. 19 is a vertical 1 section through verter having annular heat exchangeA elements; Figs. 20 and 2l are horizontal sections along Fig. 22 is a vertical section through a'modilied converter of the general type shown in Figs. 1.9-21;.` v

Figs. 23 and 24 are portions oi horizontal sections along the lines of 23-23-2424 of Fig.

22; f Fig. 25 is a vertical section of an annular 4heat exchange converter provided Withrecircuw lating and heat equalizing means; i

Figs. 26 and 27 are' portions of horizontal sec- Fig.l 25;

Fig. 28`is a section through a modified annular heat exchange converter` provided with recirculating'and heat equalizing means;

Figs. 29 and 30 are horizontal sections along the lines of 29-29-30-30 of Fig.`28;v

` Fig. 3l is avertical sectionoi a modiiied converter of the type shown in Fig/lll provided with partial recirculation;

= In the drawingsin Fig. 1 the catalyst is shown Ain `granular form but isy conventionally shown by'rstipplingin .the remaininggures. )it should be understood that the representation of the catalyst'is only a conventional.representation and `the invention is not in any sense limited to the use of .particular types orV shapes ofcatalysts.

`The converter shownon Fig. 1 consists yof an vouter shell. formed. `ofrings Y1 provided With cooled by the incoming gases.

iianges 2 and connected to a top piece 3 and bottom piece Ll. The reaction gases enter the top piece through the pipe 5, are distributed by means of the baflles-32 and thence pass down through the k central .cooling tubes 9 and then up in the outer cooling tubes 'l1 in the oppositedire'ction; The. tubes l1' are attached to theginner tubes Y 9 by any suitable fastening, such as abayonet retained by the sieve or perforated .bottom 13 through which the' reacted gases pass into the loweri space of the converter and thence out through the exhaust pipe 6. I

Catalyst can be introduced either rthroughthe sidek openings 16 or through the openings in the plate 7 which are'closed by the plugs 17. `Catalyst ycan be removedthrough the outlet 18. vThe vpipes 16 and 18 may, if desiredbe iilled with suitable inert material; Temperatures at various points are measured by the thermometric elel 1 ments 3o which are illustrated in the form of Velectric pyroriieters, but may;` of course, bemof any other suitable type.V `Where additionalcooling gases are desired atthe surface of the catalyst where the most violent reaction takes place, these gases may be introduced through the pipes 14 from the collector pipe 15.

In operation, the cold or cooled gases entering kiirst pass down through the tubes 9 in indirect heat exchanging `contact with the catalyst butin direct lheat-exchanging relation with the ascending gases in tubes l1'. gases are thus gradually warmed up andy after emerging from the open end of tubes 9; theyrise-in tubesll in direct heat exchanging relation with the catalyst and in counteriiow to the flow of gases through the catae lyst. K

bythe cooling action of the downflowing gases in tubes 9 so that thegases emerging from the top In theI case of exothermio reactions, theA catalyst is very hot and the gases in ascending/the! tubes 11 are rapidly and progressively heated, the rise in temperature beingsomewhat moderatedY of tubes 11 are not at an excessively high teYnperature. The heated reaction gases, with 'or `With-- out further addition of cool or cold gases through the pipes lil, then pass through the catalyst Where i The catalyst, however,

the reaction takes place.l

does not become overheated as it is in intimate heat exchanging relation with the tubes and is Too violent reaction in the upper rones of the catalystis efiectively prevented by the 'fact that the gases con-V tacting with the upper layers of the catalyst Vare partly cooled by the gases in the tubes 9 and may be miXed-Witha suitable amount of cold or cooler gases through the pipes 14.

It will be seen that the converter heats up in a steady, regular manner theincoming cold gases and at the same time the catalyst itself'is cooled.

`All of theheat oi the catalyst, or-y substantially jall, is thus utilized for heating the incoming gases and the manner of ,flow permits a very even cooling action, vWhile at the same time the provision or the pipes le maires it possible to control sudden increases in temperature in the-#uppercatalyst zones by'a sudden and large increase in the inflow of cold or cooler gases; Wherethe reaction doesnot produce excessive heat per unit of reactinggases or Where sudden overheating of the catalyst is not to be feared, thev auxiliary cool gas 'rstwith a'portion of thecatalyst which is at av relatively low temperature and then, as they are heated up andas they rise in the'tubes 1l, the gaseslcome into contact with progressively hotter and hotter catalyst so that at all times,4 the gases are subjected to a temperature' diierential sufficient to cause a large and steady flowo neat from the catalyst to thegases. At the same time, the

excessive temperatures which might otherwise be' producedrin the upper catalyst layers are to some extent moderated by the fact that the rising gases Anot only absorb heat from the catalyst, but alsol give off a certain increasing amount of heat to the incoming cold gases in the tubes9.

Y The converter shown in' Figari to 4 ist/ell Vsuited'for the catalytic purication of crude aromatic compounds byselective total combustion of impurities and illustrates the broad heat exchange feature of the present invention in its simplest form. Y

The catalyst for the purification of aromatic compounds may for example consist in ierrotitanium or mixtures such as for example a mixture of 8 parts` freshly precipitated Fe203 and 8 parts of TiOz suspended in 100 parts of watery and mixed with 14.2 volumes of 10 N KOH-solution, the mixture then being sprayed-onto 200 volumes Vof pea-size pumice 'fragments heated'to a temperature suiiicient to evaporatethe water as fastY as it is sprayed on.

' Theautomatic heatexchangeelements which are embedded in the catalyst are arranged and ,dimensioned so as to effect an excellent temperarture control.

vclose and herefore the contact mass surrounding the This is preferably effected by so arranging the tubes that the spaces between the end tubes 11 amount to about 2-2.45 cm.

elements is at no point more than about 2-2.5 cm. from the nearest cooling surface. Preferably the inner tubes 9 are so chosen as to jlea've as narrow an annular'space'between them asp possible in order to provide for a rapid gas 110W so that the heat exchange between the catalyst and the` reaction gases is a maximum Crude anthracene uniformly vaporized in air at 24U-260 C., in the proportion of Yone part anthracene to 20-30 parts by Weight of air enters the converters through pipe 5 and passes through the automatic heat exchange elements where it is heated up to S-400 C. by the catalyst. This rra-nge of reaction'temperatiuies is very favorable and the gases then flow through the catalyst and catalytic total combustion of some ofthe impurities, particularly carbazol, takes place, It can readily be ascertained'by the thermocouples 30 that at notime doesv the temperature exceedr 440 C; in the catalyst in normal operation.` If

, the temperature in Vthe contact mass, particularly in the upper third v`should exceed 440- C.

by reason yof abnormal operation, additional air at 250 C. can be introduced throughthe manifold 15 and pipes 14 thus adjusting the temperature both by the coolingeffect of the gas and by its diluting effect on the reaction mixture. A very uniform selective oxidationris obtained in theiconverter shown and the reaction product can be recovered either in condensing chambers or by means of steam or Water spray. The purified anthracene contains from 65-75% anthraceneand-the yields are in excess of An analysis shows that vcarbazol is substantially completely Aremoved and the main impurity remaining is phenanthrene. By recrystallization from solvent naphtha phenanthrene can be removed from the anthracenev resulting iny a eti-97% anthracene which is almost colorless and which is well suited for the production of anthraquinone. Y

instead of using crude anthracene, the product ycan first be recrystallized from solvent 'naphtha in order to first remove the phenancontaining 94-96 anthracene.

` Crude iphenanthrene may also be purified in the saine type of converten For example, phenancrude anthracene from solvent naphtha, containing about 7.5-8.5% Aanthracene,rl0.5-l1.5% carbazol and Sli-.82% phenanthrene, is purified and passed through the converter as described above. Preferably the temperature in the contact mass should not be permitted to materially exceed 400 C. The carbazol is burned out and 'a phenanthrene is obtained which contains anthracene as practically its only impurity. yThe reaction' product can then be recrystallized from alcohol which removes most of the anthracene and avery pure phenanthrene is obtained.

Crude anthraeene from other sources may be catalytically puried by the methods illustrated in Figs..1 to 4. l l

The contact mass described above and arranged as shown in Fig. 1 may also be used for the catalytic purification of crude naphthalene resulting in the selective oxidation of oily impurities such as phenol and sulfur compounds.v The reaction vconditions are obtained by vaporizing crude naphthalene with air in the proportion of 1:30 to,V 1:40 by weight and causing the mixture to entertheconverter at a temperature of M30-200 C. and in sufcient quantity to provide a very high gas speed in the automatic heat ex- Vgases after passing through the converter serve `to give up V'part of their heat to the incoming gases. The particular. design'of the heat exchanger used forms no part in the present invention and any suitable type can be used in which :the gases fiowparallel or in countercurrent. The combinationof kan external heat exchangerwith the internal vautonfiatic heat exthi-ene which is obtained by recrystallization of change elements permits avery effective tein-` perature balance and assures uniform preheating of the reaction gases to they desired reaction temperature in a simple and economical manner. Figures and illustrate modified converter forms.- Figure 5 illustrates a modification in whichthe tubes l1 extend substantially throughout'the catalyst layer and accordingly the whole of the catalyst is cooled. This construction is. v

ydesirable in certain reactions where it is nece saryv to maintain ak relatively lowl temperature The operation ofthe converter inrFig. 5

vcourse, identical with that described in Fig. l.

throughout the whole of the catalyst andwhere it is undesirable to slow up theffgas passage throughthe catalyst at any point in order to prevent side reactions or other deleterious effects. is, of

Fig. v6 shows a means of using the heat of the r .exhaust gases by extending bothtubes 9 and 11 ,haust chamber of the converter.

be provided in order to bring the exhaust gases y into more intimate heat exchanging contact with- .the tubes 11.

beyond the lower perforated plate 13 into the ex- Baffies 33 may The converter shown in Fig. 6 is of 'advantage I Where it is desired to maintain anreven tempera` ture gradient throughout the whole of the cata-4 lyst and whereit is necessary to preheat the incominggases to a relatively high temperature.V

The converter is also very advantageous for use in connection with reactions in Lwhich the final products are unstable at high temperatures and Where it is desirable toi rapidly cool the exhaust gaISGS.

The convertersshownin Figures 5 and 6 may be shown in the reaction described in connection with the converter shown lin Fig. 1. Under conditions where the materialto be ,purified isY relaf tively vunstable .the construction of Fig; 6 is.

particularly suitable 'since the `reaction products emerging .frcrn the catalyst. are immediately cooled by contact with 'the extendedautomatic heat'errchange elemental 1 Fig. l illustrates a diife'renttype,ofconverter inwhich two separate coolinggasesare usedina stead of one. The second cooling gas enters the upper converterchamber y22,througlfi the-pipe 23 andis distributedA by means of the baliies 32 to Y the tubes which are concentric'with thetubes 9. The first gas is introduced into rthe tubes 9 throughthe pipe zandupper chamber 3; Thetwo gases mix atthe bottomv of tubes 9 and20 and the mixed gases ascendthrough the tubes 11,the1 cooling effects on the catalysts being, of course. `:similar to those described in connection with l Fig. Il.v

Fig. 7 also illustrates the vuse" of two separate catalyst layers 19 and 29 vseparated by the per- Cnf fcrated plate or screen 28.y Thecatalyst 'layers f may consist, of different catalysts for effecting the Vsame reaction or they may lconsist of different catalysts for effecting different reactions.k Thus, for example, if -a'catalytic reaction proceeds in Atwo stages, the first. being strongly exothermic; and the second being vweakly exotherrnic or even andothermic, a converter such as that illustratedY in Fig. e can be very effectively used, the exo-` therinic reaction being' controlled by the cooling in the tubes and the endotherniic or the weakly exothermic reaction utilizing the heat which has been imparted to the gases byv their ypassage. `through the catalystlayer An exampleof such a reaction is the catalytic purcation ofv a crude mononuclear aromatic hydrocarbon followed by the catalytic oxidation of a side-Ychainthereof tol.

thecatalyst. v Y l.

produce an aromatic aldehyde or ketone. Obvi-` ously, of course, the arrangement of layers can lne-reversed andmore than two layers can be used. The use of a plurality of layers is also not limited to the particular cooling tube construction shown in 9 and can be rapplied tothe cooling construction shown. in the other figures.y An attempt has been made yto illustrate as many conaspects these combinationsare included within.

the purview of the invention.

Fig. 8 illustrates a converter provided with means for introducing two gases, one-from the spaceS into the tube 9 has been described lin previous figures, and another portion of gas through the pipe which gas is distributed by the baffles However, in certain gures, cer-fifi 26 and passes `down through the pipes 27 directly or cooler gases strikes the upper portionof the catalyst. This type of converter is very usefulv in reactions where a great portion of the heat is .developed in the iirst few inches of` catalyst into the catalyst space so that a stream of cold.

and overheating'is prevented 'by `the streams of.

` relatively cold gas strikingthis hot portion of the catalyst. A very even and `efficient control of temperature can be brought about by means of this type of converter and where the gases entering thespace 3 are preheated they serve to slightly heat the cooler gases passing throughthe pipes 27 and are at the same time somewhat cooled".

down. The hot gases emerging from the pipes l1 also mix immediately with the cooler gases from the pipes 27 and a uniform temperature.`

control can be easily effected. v

. A similar design of converter is shown in Figi". `9 but the mixing of gases coming from the pipes 27 with the gases emerging from the pipes llis eifected by causingl the gases-to emerge from thev pipes 27 lin a more or less horizontal direction.

This is brought about by removable bottoms 38 in the pipes 27 .which force the gases to pass out through the perforations 39 in the tubes, thus effecting a more uniform mixture of the two gSes and preventing jets of relatively cold gas from striking the catalyst surface, as may readily occur in the design shown in Fig. 8 when the gas velocities through the pipes 27 are high. A detail viewV of the bottom of thepipes 2.7l is shown in Fig. 15. The converter shown in Fig. 9 also illustrates the use of two different layers of catalyst, onel layer being cooled by the tubes 1l and the other being unccoledf In both figures 8 and 9, the catalyst can be charged linto the converter not only through the chargingopening 16 but also l'through the pipes 27 after removing the bottoms 38 in the caseof the converter shown in Fig. 9. It is advantageous for some purposes-'to charge through these tubes in order to effect a more uniform distributionof` catalyst.

Fig. 10 shows a detail of the tubes27provided Vwith, the'v baffle plates 38 and perforations 39,

whichpieventy a blastlof cold gas directly striking show converter and' gas Figures '7, .8 and 9 introducing arrangementsvvhich are suitable for purifications in which the material to be puriiied is very resistant to decomposition inthe presence of the catalyst usedl Thusfor example,"y by use of specially damped catalysts'particularly in the uncooled catalyst layers, reactionssuch as the catalytic-purification of anthracene under conditionsdescribed above may be carried out, particularly where the catalyst power varies in the direction of gas ilow or the catalysts possess different specific activities. t

Y The particular construction shown in Figs. 8

and 9 permits adjustment of the temperature of the4 gases after passing through the automatic the Y' direct heat exchange elements before they contact with ythe catalysts, this adjustment being effected by introduction of additional gases through the-tubes 27. This possibility of adjustinent is very important, as the initial teinperature of the gases contacting withthe contact mass is one of the mostlimportant controllablev factors. Not only can the temperature of the reaction gases be Varied at will but the concen- Ytration can be varied by the addition yor" different f amounts of auxiliary gases, which results in a very desirable flexibility of'converter operation.

Fig. 11 showsamodiication somewhat similar to that of Fig. 9 but instead-of using an outer tube 11 open at the top in the'autom'atic heat exchange elements, this tube is closed at the top and isprovided with suitable perforations just below the level of the catalysts so that the heated. gases pass outinto ythe, catalyst without mixing with theV cool gases coming through` pipes 27. The inner tube 9 is shown perforated but may also be solid with openr bottom. The perforation of the inner l'tube 9 permits the incoming gases to escapey over a larger Yarea and therefore preventsrcreatio'n of a Acold spot at the bottom of tube 11-v as' sometimes may take placefwhen the full blast of the incoming gases strikes the bottorn of this tube. n

The"ar`rangement shownA in Fig. 11 is well adaptedfor catalytic purification of crudeanthracene or of crude naphthalene, The perforations of the innertube permit very uniform cooling of the contact massV and the perforationsin thetube vll permit'the gas topass into the contact mass throughout a larger areavand therefore Y prevent accumulations of heat at the point where gases rst encounter the catalysts and where, of course, the reaction and consequently the evol u"v tion of heat is a maximum owing to the high This ar-' concentration of reacting components. rangement also permits a very satisfactoryncontrol of the compositiontand speed of flow of the gases.

Since the converters used in carrying out the' i processofthe present'invention are of exceedingly cheap construction and do not require gas tightness in the ,heat Vexchange "elements, it A is advisable to work with largevamounts of catalysts and spread'the reaction over a large amount of permits high yields. f

Contact mass, for example'y by increased Velocity of gases which may be effected 'by greater Aair dilution* Inthis manner the strongly'exothermie "catalytic: reactioncan be carried out under convditions which do rnottavor` local over-heating and theautomatic heat exchange elements' serve toV maintain a uniformreaction condition i'ivhichv he spacingof the external tubes of the ,automatic heat exchange elements shouldpreferably not exceed 3 cm. as the heat conductivity of the r,icatalyst is not Veryhigh and a' uniform temperaturethroughout the catalyst can not be obtained if tlie heat exchange elements are placed too far apart. t

Figs. 19 to 24 show a type of converter in which the flow of the gases in heat exchanging relation withl a catalyst follows the same principles as in Figs. 1 to 11 but the converter arrangement is quite different.' As in Fig. 1, the converter consists'in a shell 1 and top piece 3, bottom Vpiece 4, gas entrance pipe 5, exit pipes 6, distributing baille plates 32. Instead of providing a 2- partition inthe upper portion of the converter in which the automatic heatexchange elements are hung, a similar effect is obtained by providing annuli with' one end open and being of different size and arranged to nt into each other. shorter concentric annuli 4.0 are nested with their closed ends resting ona perforated bottom support 41 and larger annuli 42 are likewise nested with their open ends, which are preferably perforated,"fittingv into the 'open ends of annuli 40.

It will be apparent, of course, that the center of the annuli 40 is taken up with an open end tube 43 and the outermost annuli, both long and short, are halved and utilize the converter shell 1 as one of their walls.r These built-up annuli are numbered 44 and 45 respectively. The catalyst is placedb'etween the annuli 40. Vhile the con- Yverter structure is radically different from that shown in Fig. 1, an examination of the vertical cross section inf Fig. 19 'will make it apparent that the gas flowris the same, that is to saythe lincoming gases through the pipe 5 ilow down the annular spaces between the annuli 42, reverse their ow and pass up between the walls o1 the annuli 42V and4 the annuli 40; or in the case of the central annulus '42 the lgases pass 'down through the tube '43, reverse their flow and pass up through `the annular space between this tube and the closed 'end tube 43. The first ow is in indirect heat exchanging relationwith the catalyst andon reversal of ilow the gases pass in 'direct heat exchangingrelation 'with the catalyst and also with the'incoming gases on the down flow andthen on'a second reversal the gases pass through the catalyst. In other words, in Fig. V19 instead vof a series of circular automatic heat vexchange elements'lwithr-double counter flow all but one of the heat exchange elements are annular insteadof circular. This construction presents some advantages foi`- certain converter sizes and thecontrol dueto the fact that a surface of heatexchange element in contact with catalyst compared to catalyst volume is greater than with circular elements of the same area, and somewhat more uniform control of the heat evolved may be obtained and is of importance in many can be usedrfor the reactions described in connection Vwith the converter shown in Figs. 1 to 11V under lthe 'reaction' conditions therein set forth andare particularly effective for the catalytic purii'ication of crude aromatic hydrocarbons, such as Yforexarnple transforming crude anthracene into high grade anthracene; crude naphthalene into highly purified naphthalene, 

